This invention relates to improved apparatus of the rotary arc type for severing elongated material, such as round tubing, moving continuously of its length.
Rotary arc cutoff apparatus for severing metal tubing, roll-formed shapes and elongated extruded workpieces typically comprises a cutoff die set mounted for substantially linear reciprocating movement along tracks on the flat bed of a mechanical pres with a long, relatively heavy, ram moving with and causing a clamping and cutoff blade assembly associated with the die set to engage and sever the workpiece. A plurality of links are pivotably connected at their opposite respective ends to the press and the ram such that driving rotation of an eccentric crank connecting the ram to the press imparts swinging oscillatory motion to the ram whereby when the die set is accelerated up to that of the tube the cutoff blade reciprocates vertically relative to the die set.
In Borzym "Flying Cutoff Machine with Swinging Ram" U.S. Pat. No. 3,288,011 issued Nov. 29, 1966 the crank is pivotally connected to only one of the four links which connection limits the vertical rise of the ram. In general, the vertical rise of the ram correlates into longer strokes and greater tube diameters that can be cut. The length of the links would have to be increased to increase the tube diameters which can be cut. However, the driving connection between the crank and ram places a limit on the upward vertical movement of the ram and this limits the work that can be done. A ram which has greater vertical stroke and decreased inertia to allow for faster response in its stroke would be desirable.
In Riera et al. "Flying Cutoff Machine" U.S. Pat. No. 4,354,409 issued Oct. 19, 1982, specifically incorporated herein by reference, the ram is driven by a central crank assembly to impart an orbital movement to the ram and includes a slide member mounted thereto for sliding movement relative to the ram. Orbital movement of the ram permits cutting of heavier metals at higher speeds because the ram is traveling in the direction of the moving material during the cutting operation. Sliding contact between the metal surfaces over the entire stroke of the press causes high friction and inertia. Turning of the crank at very high RPM imposes a turning moment on the ram which can result in chattering effect wherein the ram experiences slight angular displacements along the ram longitudinal axis. As a result, available power to drive the ram may be consumed. It would be desirable to have a sliding connection between the link and ram which minimizes movement and friction which would correlate in a lower power required to move the ram in the orbital path. It would also be desirable to reduce the weight of the ram and its support apparatus whereby to further reduce the power required to drive the ram. The invention provides a ram assembly which has a faster response to its orbiting motion, and reduces power required to orbit the ram in parallel planes relative to a tube cutoff die set. The ram is constrained by a slide assembly for horizontal swinging movement without introducing wear on the ram. Without increase in link length, the present invention increases the vertical workstroke of the ram, to allow the severing of tubing having larger diameter and to increase the linear speed of th die relative to the longer bed.
Advantageously such a ram assembly would retrofit the prior cutoff machine of Riera et al. U.S. Pat. No. 4,354,409 without substantially redesigning same.
Other features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiment of the invention taken in conjunction with the accompanying drawings.